Self-Efficacy Based Treatment for Long-term Weight Loss Obesity is a major, chronic health problem associated with an extremely high rate of relapse. Approximately 80% of of adults who intentionally lose weight regain 50% of the weight within a year. Standard behavioral treatment (SBT) protocols have been used in clinical trials of weight loss for nearly two decades with little improvement in the rates of weight loss maintenance. There is increasing evidence that self-efficacy, one's perception of his capability to perform certain behaviors, is a factor that influences weight loss maintenance and a focus on enhancing self-efficacy might alter outcomes. The strongest of the four sources of selfefficacy enhancement is mastery performance. While an SBT program provides standard goals for all participants, it does not use a tailored approach nor does it set goals in an incremental manner to increase the likelihood of performance mastery occurring. The intervention in the proposed study will be operationalized to build on the four sources of self-efficacy in order to enhance participants' perceptions of their capability to make and sustain lifestyle changes. We propose to conduct a two-group randomized controlled study: the experimental group will consist of a modified SBT weight loss intervention - it will deliver the standard content in group sessions but be supplemented by individual sessions guided by selfefficacy theory and provide tailored, incremental goals for weight loss and accordingly incremental calorie and fat restriction goals (SE + mSBT) that will be increased as the goals are achieved; the comparison group will receive an SBT weight loss intervention that will be delivered in group sessions and provide standard calorie and fat restriction goals that are based on baseline weight (< or =/> 200 Ibs). We hypothesize that the experimental group will have improved weight loss maintenance, quality of life, adherence to lifestyle change, and a reduced coronary heart disease (CHD) risk profile. The sample of 120 adults will have a body mass index between 27 and 43 and at least two risk factors for CHD. The intervention will last 18 months and assessments will be conducted at 0, 6, 12, and 18 months. If demonstrated to have efficacy in maintaining weight loss, the proposed intervention could reduce the rate of recidivism following weight loss treatment and be considered for translation to clinical practice sites.